CN116355699A - Method for preparing biodiesel by catalyzing waste grease through zinc glycerate - Google Patents
Method for preparing biodiesel by catalyzing waste grease through zinc glycerate Download PDFInfo
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- CN116355699A CN116355699A CN202211608905.8A CN202211608905A CN116355699A CN 116355699 A CN116355699 A CN 116355699A CN 202211608905 A CN202211608905 A CN 202211608905A CN 116355699 A CN116355699 A CN 116355699A
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- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
- C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
- C11C3/04—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fats or fatty oils
- C11C3/06—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fats or fatty oils with glycerol
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L1/00—Liquid carbonaceous fuels
- C10L1/02—Liquid carbonaceous fuels essentially based on components consisting of carbon, hydrogen, and oxygen only
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- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
- C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
- C11C3/04—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fats or fatty oils
- C11C3/10—Ester interchange
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/10—Biofuels, e.g. bio-diesel
Abstract
The invention discloses a method for preparing biodiesel by catalyzing waste grease with zinc glycerate, which comprises the steps of pretreating raw material waste grease, performing glycerol esterification reaction, performing transesterification reaction and performing post-treatment to obtain BD100 biodiesel; the glycerin esterification reaction and the transesterification reaction processes all adopt glycerin zinc catalysts, the glycerin zinc catalysts react with free fatty acid to form fatty acid zinc, homogeneous catalysis of the glycerin esterification and transesterification reaction processes is realized, the fatty acid zinc and glycerin react to regenerate glycerin zinc in the later reaction period, and the glycerin esterification catalyst has the advantages of easiness in separation of heterogeneous catalysts and the characteristics of high efficiency of homogeneous catalysts. The invention skillfully combines the transformation characteristics of zinc glycerate and zinc fatty acid based on the amphoteric catalysis characteristics of zinc glycerate, couples the glycerol esterification reaction and the transesterification reaction of waste grease, realizes the homogeneous catalysis reaction process and the heterogeneous separation process of a heterogeneous catalyst, has the characteristics of high reaction rate, recyclable catalyst and the like, is suitable for industrial production, and can stably produce BD100 biodiesel.
Description
Technical Field
The invention belongs to the technical field of grease chemical industry, and particularly relates to a method for preparing biodiesel by catalyzing waste grease through zinc glycerate.
Background
Biodiesel is a clean and green fuel because of its sustainability, low sulfur content, and biodegradability. At present, waste grease is the main raw material of the existing biodiesel enterprises in China. However, the waste grease contains a large amount of free fatty acid, and the biodiesel is obtained through acid reduction pretreatment and then base catalytic transesterification. At present, the biodiesel is generally prepared by a two-step method of sulfuric acid catalytic esterification reaction and homogeneous alkali (KOH, naOH and the like) catalytic transesterification reaction in industrial production of biodiesel, and the method has the common problems of large sulfuric acid wastewater amount, serious equipment corrosion, over high washing cost, lower biodiesel yield and the like.
The glycerol esterification method is an effective acid reduction method, can reduce the acid value in the high acid value grease to below 1mgKOH/g, can reduce the acid more thoroughly, and simultaneously avoids the problems of a large amount of sulfuric acid wastewater, equipment corrosion and lower biodiesel yield, and the byproduct glycerol after transesterification can be recycled as a glycerol esterification raw material through refining.
However, in the actual production process, the glycerol esterification method still has the problems of larger energy consumption, large oil evaporation loss, more glycerol polymerization and the like (the general reaction temperature is 220-240 ℃), so that the content of organic matters in the glycerol esterification wastewater is higher, the glycerol recovery rate is lower, and the biodiesel yield is lower; in addition, the transesterification reaction process is catalyzed by homogeneous alkali (KOH or NaOH), and the problems of easy saponification of grease, low biodiesel yield, difficult catalyst recovery, high glycerol refining cost and the like still exist.
Disclosure of Invention
Aiming at the technical problems in the prior art, the purpose of the application is to provide a method for preparing biodiesel by catalyzing waste grease with zinc glycerate. In the method, both the glycerol esterification reaction and the transesterification reaction are carried out under the catalysis of zinc glycerate, and the zinc glycerate can react with fatty acid in the waste grease of the raw materials to generate soluble fatty acid zinc, so that zinc element exists in the form of fatty acid zinc to realize homogeneous catalytic esterification. The invention further controls the acid value of the feed liquid after the glycerol esterification reaction to be in a certain range, is favorable for continuous homogeneous catalysis of part of zinc elements in the transesterification reaction, has the acid value of less than 0.5mgKOH/g after the reaction is finished, and basically converts the zinc elements into zinc glycerate to be separated out, thereby realizing the homogeneous catalysis reaction process and the heterogeneous separation process of the heterogeneous catalyst.
The technical scheme that this application adopted is:
a method for preparing biodiesel by catalyzing waste grease with zinc glycerate comprises the following steps: the BD100 biodiesel is obtained by the steps of pretreatment, glycerol esterification reaction, transesterification reaction and post-treatment of the waste oil as raw material; the pretreatment process adopts an organic extractant to extract waste grease, and after impurities are removed by filtration, the organic extractant is removed to obtain glycerin esterification raw materials, and the organic extractant is reused in the raw material pretreatment process; the glycerol esterification reaction and the transesterification reaction are both carried out under the catalysis of zinc glycerate, the zinc glycerate catalyst reacts with free fatty acid to form zinc fatty acid, the homogeneous catalysis of the glycerol esterification and the transesterification reaction is realized, the zinc glycerate is regenerated by the reaction of the zinc fatty acid and the glycerol in the later period of the reaction, and the method has the advantages of easiness in separation of a heterogeneous catalyst and the characteristics of high efficiency of a homogeneous catalyst. The post-treatment process comprises four processes of catalyst sedimentation separation, flash evaporation dealcoholization, glycerin sedimentation separation, rectification and purification, the liquid after transesterification reaction is subjected to post-treatment procedures to obtain a high-quality BD100 biodiesel product, and meanwhile, the separated zinc glycerate catalyst, methanol and glycerin are recycled in the biodiesel production process.
Further, the organic extractant adopted in the pretreatment process is n-hexane.
Further, the waste grease comprises at least one of nigre acidification oil and kitchen waste oil, and the waste grease contains free fatty acid, and the acid value of the waste grease is in the range of 20-180 mgKOH/g.
Further, the glycerol esterification reaction procedure is to mix the pretreated waste grease with glycerol and a glycerol zinc catalyst for reaction at 160-200 ℃, preferably 165-170 ℃, wherein the glycerol is 10-25 wt%, preferably 12-15 wt% of the oil weight, the catalyst is 1-3 wt%, preferably 1.5-2.0 wt% of the oil weight, and the reaction time is 0.5-2 h, preferably 1-1.5 h.
Further, the acid value of the feed liquid after the glycerol esterification reaction is controlled to be in the range of 5-20 mgKOH/g.
Further, the transesterification reaction procedure is to mix and react feed liquid methanol after the glycerol esterification reaction, and the reaction is carried out under the nitrogen atmosphere, wherein the reaction temperature is 100-150 ℃, preferably 130-140 ℃, the reaction pressure is 0.4-1.1MPa, preferably 0.8-1.0MPa, the molar ratio of methanol to the alcohol oil of the waste oil and fat of the initial raw materials is 20:1-35:1, preferably 28-30:1, and the reaction time is 1-3h, preferably 1.5-2h.
Further, the acid value of the material liquid after the transesterification reaction is controlled to 1mgKOH/g or less, more preferably 0.5mgKOH/g or less.
Further, the zinc glycerate catalyst is prepared by reacting zinc acetate dihydrate with glycerol and deionized water at 140-160 ℃, and the molar ratio of the zinc acetate dihydrate to the glycerol to the deionized water is controlled to be 1 (70-80) (5-7); the reaction temperature is preferably 150 ℃, and the molar ratio of zinc acetate dihydrate to glycerol to deionized water is preferably 1:75:6.
The beneficial effects obtained by the invention are as follows:
(1) The invention skillfully combines the transformation characteristics of zinc glycerate and zinc fatty acid based on the amphoteric catalysis characteristics of zinc glycerate, couples the glycerol esterification reaction and the transesterification reaction of waste grease, realizes a homogeneous catalysis reaction process and a heterogeneous separation process which are not possessed by the traditional heterogeneous catalyst, has the characteristics of good raw material universality, environment-friendly process, high reaction rate, high product yield, recyclable catalyst, suitability for industrial production and the like, and can stably produce BD100 biodiesel.
(2) The invention uses the simply synthesized zinc glycerate as the catalyst, is applied to the process of preparing biodiesel by catalyzing the esterification and transesterification of the waste grease glycerin, realizes the acid-base integrated catalysis, avoids the occurrence of side reactions such as grease saponification, reduces glycerin polymerization and simplifies the glycerin separation process.
Drawings
FIG. 1 is a flow chart of preparing biodiesel by catalyzing waste grease with zinc glycerate;
FIG. 2 is an SEM image of a zinc glycerolate catalyst obtained in example 1;
FIG. 3 is a TEM image of the zinc glycerolate catalyst obtained in example 1.
Detailed Description
The invention will be further illustrated with reference to specific examples, but the scope of the invention is not limited thereto.
Example 1: preparation of the catalyst
8.00g zinc acetate dihydrate, 200ml glycerol and 4ml deionized water (molar ratio 1:77:6.22) are heated, stirred and refluxed for 1 hour at 160 ℃, solids are collected by filtration, and the solids are washed by the deionized water and ethanol and dried to constant weight, so that the zinc glycerate catalyst is obtained, the analysis results of the obtained zinc glycerate SEM and TEM are shown in fig. 2 and 3, and the performance parameters are shown in table 1.
TABLE 1 Performance parameters of zinc glycerate catalysts
Example 2: glycerol esterification reaction of waste grease catalyzed by zinc glycerate
Preheating 500g of palmitoylated oil (with an acid value of 113 mgKOH/g) to 170 ℃, adding glycerol (125 g, 25% of the weight of the raw oil) and a zinc glycerinum catalyst (10 g, 2% of the weight of the raw oil) to carry out glycerinum esterification reaction, controlling the reaction temperature to 170 ℃, controlling the reaction time to 2 hours, and enabling the final acid value to be smaller than 1mgKOH/g of oil; the reacted materials are filtered and separated to obtain the glycerinum (the recovery rate of the glycerinum can be stabilized at 95%), and the glycerinum is continuously applied to the glycerinum esterification reaction after being washed, dried and recovered by deionized water and ethanol, and the experimental results of the glycerinum esterification reaction of the glycerinum catalytic palmitoylated oil are shown in the table 2:
TABLE 2 experimental results for the glycerol esterification reaction of zinc glycerate catalyzed palmitoylated oil
Example 3: the zinc glycerate catalyst catalyzes the transesterification reaction of waste grease:
40g of the esterified feed liquid (the fatty acid content is 10% of the oil weight), 43.63g of methanol (the molar ratio of alcohol to oil is 30:1) and 1.2g of zinc glycerolate (3% of the oil weight) are added into an autoclave, pressurized to 1.1MPa by nitrogen, and then heated to 140 ℃ for transesterification, the reaction time is 2 hours, and the biodiesel yield is 90.1% after the reaction is finished.
Example 4: the preparation of the biodiesel comprises the following steps (the process flow is shown in figure 1):
1) Pretreatment: the biodiesel feedstock used in example 4 was swill-cooked dirty oil (with fatty acid profile as shown in table 3) and its pretreatment steps were as follows: 500mL of swill-cooked dirty oil is heated to liquid state, extracted by using equal volume of normal hexane, filtered to remove solid impurities, and flash distilled to remove normal hexane to obtain glycerin esterification raw material (the flash evaporation vacuum degree is 0.01MPa, and the flash evaporation temperature is 60 ℃). The distribution of fatty acid composition of the pretreated swill-cooked dirty oil and the corresponding indexes of swill-cooked dirty oil before and after pretreatment are shown in table 4:
TABLE 3 distribution of fatty acids in swill-cooked dirty oil
TABLE 4 comparison Table before and after pretreatment of illegal cooking oil
2) Glycerol esterification reaction: preheating 500g of pretreated swill-cooked dirty oil to 170 ℃, adding glycerol (the glycerol amount is 20% of the weight of the raw oil, 100 g) and a zinc glycerate catalyst (the catalyst amount is 3% of the weight of the oil, 15 g) to carry out glycerolysis reaction, controlling the reaction temperature to 170 ℃, controlling the reaction time to 1 hour, and finally controlling the acid value to 20mgKOH/g; 3) transesterification: after the material liquid after the glycerol esterification reaction is cooled to 60 ℃, the material liquid is conveyed into a high-pressure reaction kettle, methanol (the molar ratio of the methanol consumption to the raw material swill-cooked dirty oil is 30:1) is added, the temperature is raised to 140 ℃ after the nitrogen is pressurized to 1.1MPa, the transesterification reaction is carried out, the reaction time is 2 hours, the final acid value is less than 0.5mgKOH/g, and the biodiesel yield is about 92% after the reaction is finished.
4) Post-treatment: separating the material after transesterification by sedimentation to obtain a zinc glycerate catalyst, wherein the recovery rate of the zinc glycerate reaches 96%, and the zinc glycerate catalyst can be reused for glycerol esterification reaction; flash dealcoholization (flash vacuum degree 0.01MPa, flash temperature 60 ℃) is carried out on the material from which the catalyst is separated while the material is hot, and the separated crude methanol can be reused for transesterification after being rectified by methanol; the dealcoholized feed liquid is further settled, wherein the upper crude methyl ester is rectified under the pressure of 500Pa to obtain a biodiesel product, and the quality analysis result of the obtained biodiesel is shown in table 5; the refined glycerol can be obtained after the lower crude glycerol is rectified and is used for the glycerol esterification reaction and the catalyst preparation; the plant asphalt and the glycerol asphalt obtained from the tower kettle after rectifying the crude methyl ester and the crude glycerol can be further recycled.
TABLE 5 analysis results of biodiesel products
In conclusion, the zinc glycerolate has higher catalytic activity and higher catalytic stability in the catalytic esterification and transesterification reaction of waste grease, and finally the BD100 biodiesel and GB 25199-2017 standard are obtained.
What has been described in this specification is merely an enumeration of possible forms of implementation for the inventive concept and may not be considered limiting of the scope of the present invention to the specific forms set forth in the examples.
Claims (8)
1. The method for preparing biodiesel by catalyzing waste grease with zinc glycerate is characterized by comprising the following steps: the BD100 biodiesel is obtained by the steps of pretreatment, glycerol esterification reaction, transesterification reaction and post-treatment of the waste oil as raw material; the pretreatment process adopts an organic extractant to extract waste grease, and after impurities are removed by filtration, the organic extractant is removed to obtain glycerin esterification raw materials, and the organic extractant is reused in the raw material pretreatment process; the glycerol esterification reaction and the transesterification reaction are both carried out under the catalysis of zinc glycerate, so that the homogeneous catalysis reaction process of zinc element in the reaction and the heterogeneous separation process in the subsequent post-treatment are realized; the post-treatment process comprises four processes of catalyst sedimentation separation, flash evaporation dealcoholization, glycerin sedimentation separation, rectification and purification, the liquid after transesterification reaction is subjected to post-treatment procedures to obtain a high-quality BD100 biodiesel product, and meanwhile, the separated zinc glycerate catalyst, methanol and glycerin are recycled in the biodiesel production process.
2. The method for preparing biodiesel by catalyzing waste grease with zinc glycerate according to claim 1 is characterized in that the organic extractant adopted in the pretreatment process is n-hexane.
3. The method for preparing biodiesel by catalyzing waste grease with zinc glycerate as claimed in claim 1, wherein the waste grease comprises at least one of soapstock acidification oil and kitchen waste oil, and the waste grease contains free fatty acid, and the acid value of the waste grease is in the range of 20-180 mgKOH/g.
4. The method for preparing biodiesel by catalyzing waste grease by using zinc glycerate as claimed in claim 1, wherein the glycerol esterification reaction procedure is characterized in that the pretreated waste grease is mixed with glycerol and a zinc glycerate catalyst for reaction at a reaction temperature of 160-200 ℃, preferably 165-170 ℃, the glycerol amount is 10-25 wt%, preferably 12-15 wt% and the catalyst amount is 1-3 wt%, preferably 1.5-2.0 wt% and the reaction time is 0.5-2 h, preferably 1-1.5 h.
5. The method for preparing biodiesel by catalyzing waste grease with zinc glycerate according to claim 1 is characterized in that the acid value of the feed liquid after the glycerol esterification reaction is controlled within the range of 5-20 mgKOH/g.
6. The method for preparing biodiesel by catalyzing waste grease with zinc glycerate according to claim 1 is characterized in that the transesterification reaction procedure is carried out by mixing methanol in the liquid material after the esterification reaction of glycerol under nitrogen atmosphere, the reaction temperature is 100-150 ℃, preferably 130-140 ℃, the reaction pressure is 0.4-1.1MPa, preferably 0.8-1.0MPa, the molar ratio of methanol to alcohol oil of the waste grease of the initial raw material is 20:1-35:1, preferably 28-30:1, and the reaction time is 1-3h, preferably 1.5-2h.
7. The method for preparing biodiesel by catalyzing waste grease with zinc glycerate as claimed in claim 1, wherein the acid value of the liquid after transesterification is controlled below 1mgKOH/g, preferably below 0.5 mgKOH/g.
8. The method for preparing biodiesel by catalyzing waste grease with zinc glycerate according to claim 1 is characterized in that the zinc glycerate catalyst is prepared by reacting zinc acetate dihydrate with glycerol and deionized water at 140-160 ℃, and the molar ratio of zinc acetate dihydrate, glycerol and deionized water is controlled at 1 (70-80): 5-7); the reaction temperature is preferably 150 ℃, and the molar ratio of zinc acetate dihydrate to glycerol to deionized water is preferably 1:75:6.
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